inpatient / Pulmonology and critical care

Respiratory Failure and Intubation

Last Updated: 12/25/22

# Acute Hypoxic/Hypercarbic *** Respiratory Failure 2/2 ***

-- ABCs: ***
 pulse ox, ABG - does the patient need to go to the ICU for monitoring or be intubated in the near-term
-- Chart Check: home O2 use, previous intubations, underlying pulm disease, right heart function (previous echo), meds,
-- HPI Intake: ***
-- Can't Miss: *** PE and right heart strain (may decompensate if intubated), ARDS (avoid barotrauma), tension PTX, opioid overdose, anaphylaxis, stroke, carbon-monoxide toxicity
-- Admission Orders: CBC, BMP, ABG, EKG, continuous pulse ox, tele; consider trop, BNP, dimer, need for CT chest
-- Initial Treatment to Consider: treat underlying etiology (diuresis, abx, steroids, vasodilators), consider need for HFNC

-- History: ***
-- Clinical: *** SOB, cough, chest pain, somnolence, anxiety, headache,
-- Exam: *** WOB (nasal flare, pursed lips, accessory muscle use, retraction, tripoding), secretions, rhonchi/wheezing, crackles, AMS
-- Data: *** SpO2, ABG, lactate, CXR, cultures
-- Etiology/DDx: Hypoxemia: edema, PNA, ARDS, PTX, PAH, PE; Hypercarbia: COPD, asthma bronchiectasis/CF, angioedema, OSA, laryngospasm, CNS depression (opioids, TBI, cerebral hernitation), resp muscle weakness; Tachypnea: acidosis, shock, anxiety

The patient's HPI is notable for ***. Exam showed ***. Labwork and data were notable for ***. Taken together, the patient's presentation is most concerning for ***, with a differential including ***.

-- CT chest if unsure of underlying etiology
-- Trend ABG/VBG, lactate
-- Daily CXR

-- Vent Settings: Vt: *** RR *** PEEP *** FiO2 ***; change *** to ***
-- Sedation: RASS goal *** ; *** (propofol, dexmedetomidine/precedex, midazolam; refractory agitation - quetiapine, haldol )
-- Analgesia: *** (fentanyl 25-50mcg bolus, 50-200/h; dilaudid, morphine)
-- Volume: *** 
-- Barriers for Extubation: *** (tx etiology, P:F>150, PEEP <=5, FiO2 <=0.4, pH>7.25, can cough, secretions, HD stable off pressors, ideally alert, follow commands)
-- SAT/SBT *** (30-120 min SBT trials daily with PEEP <=5 - increase timing)
-- Secretions: *** (nebs, acetylcysteine/mucomyst, glycopyrrolate, steroids)
-- If expected intubation >14 days, discuss tracheostomy


The patient remains intubated due to *** (ARDS, PNA, COPD, AMS, etc)
They have the following vent settings: ***  (Mode / Tidal Volume / RR / PEEP / FiO2)
On these settings, the ABG is *** (pH / pCO2 / paO2 / sat)
The patient's oxygenation is *** (improving / worsening) and the CXR is *** (better / worse)
To improve oxygenation I propose we *** (diurese, FiO2, PEEP, etc)
To improve ventilation I propose we *** (RR, Vt, prone, etc) 
We should continue *** to treat *** 
We should send/follow up *** to further work up the etiology of respiratory failure.
We are *** ready for spontaneous breathing trial today; limiting factors may include *** (oxygenation, ventilation, neuro status, airway).
Current sedation is ***.
We are *** at goal OR should make the following changes ***.

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If You Remember Nothing Else

If a patient is showing evidence of respiratory failure, do not wait to intubate. Start with AC/VC with lung-protective settings until you understand the etiology. Start with propofol and precedex for sedation and fentanyl for analgesia. Oxygenatin is driven by FiO2 and PEEP; ventilation is driven by RR and tidal volume (Vt). High peak pressure but low pplat suggests increased airway resistance; high peak and high pplat suggest low lung complicnace. Auto-PEEP is incomplete alveolar emptying - decrease RR to decrease I:E ratio. The requirements for extubation include: addressing the etiology of respiratory failure, managing O2 and CO2 (PEEP <=5, FiO2 <=0.4, pH >7.25), cough intact, secretions manageable, HD stable, ideally alert and following commands. Perform SBTs daily - causes of failure include ongoing underyling process, overload, weakness, delirium, anxiety, metabolic causes.

Clinical Pearls

  • Respiratory failure happens when the respiratory system cannot maintain gas exchange (PaO2 < 60 mm Hg, PaCO2 > 50 mm Hg) in either the chronic or acute setting
  • Indications for endotracheal intubation include airway obstruction (anaphylaxis, angioedema), airway protection (AMS, hematemesis, vomiting, secretions), and need for mechanical ventilation (respiratory failure, septic shock, trauma)
  • Ventilation determines PaCO2 - increasing RR and Vt increases ventilation and lowers PaCO2; in general start with RR first to keep Vt below 6cc/kg (a goal Vt of <6cc/kg decreases mortality in ARDS), do not go over 30-35 as will lower expiratory time leading to air trapping and auto-PEEP; make sure Pplat <30 and driving pressure <15
  • Oxygenation determines PaO2 - increasing FiO2 and PEEP increases oxygenation and increases PaO2; in general avoid FiO2 >0.6 due to toxicity; PEEP increases recruitment
  • If you increase PEEP and P:F does not go up or PaCO2 increases, you are not recruiting and instead increasing dead space and should decrease the PEEP
  • AC/VC - assist control volume control - delivers breath until set Vt reached - usually where you start with acute resp failure - gives you the most control, avoid barotrauma but setting a fixed inspiratory volume increases dyssynchrony; you essentially set everything, most notably Vt
  • PSV - pressure support - deliver set pressure triggered by spontaneous breath - you set the pressure and backup RR; usually when intubated for non-pulm etiology or when weaning the vent - better tolerated, don’t need as much sedation, good for trialing pre-extubation, but no fixed RR and less control over parameters 
  • When doing a spontaneous breathing trial, usually keep 5/5 (Pinsp/PEEP) to help overcome extra resistance of the tubing
  • Inspiratory hold - able to measure Pplat which is the elastic pressure of the lung which measures the lung compliance
  • If high peak but normal Pplat, there is increased resistance in the airway - biting tube, obstruction, bronchospasm, secretions; if high peak and high Pplat >30, low lung compliance - most often caused by edema, ILD, PNA, PTX, auto-PEEP, asynchronous breathing
  • Expiratory hold - able to quantify the auto-PEEP which measures hyperinflation 2/2 incomplete alveolar emptying (often caused by higher RR or obstructive disease)
  • auto-PEEP can lead to hypotension due to increased intrathoracic pressure which decreased venous return and thus preload; treat by decreasing RR or decreasing I:E ratio (which decreasing RR does)
  • auto-PEEP is one of the reasons we disconnect patients from the ventilator and bag them when there is HD compromise - allows deflation if the hyperinflation was contributing
  • Complications of intubation include hypotension, VAP, laryngeal edema, tracheal stenosis
  • Requirements for extubation - etiology of resp failure treated, O2/CO2 (P:F>150, PEEP <=5, FiO2 <=0.4, pH>7.25), can cough, secretions manageable, HD stable, ideally alert, following commands though not required
  • Though unintuitive, due to the need to be aggressive with extubating patients, there is an acceptable risk for failure; and most ciritcal care sources align around ~15% as reasonable
  • You should check for a cuff leak if there are any risk factors for laryngeal edema: traumatic intubation, intubated >6 days, large ET tube, re-intubation, women; if there is no leak, give 60mg IV methypred once (peak effect within ~4ish hours, half-life of 4 hours) and then extubate 4-6 hours after (do not check again for cuff leak - it has only been validated prior to use of steroids)
  • Suprisingly there is no standard definition of a cuff leak - in general, consider it positive if you hear an audible leak which is probably the most reproducible way to do it; you can also look to see if there is a loss in volume of >110mL or >24% of the tidal volume (volume loss is difference between inspired and exhaled volume)
  • RR/Vt - if ratio >105, predicts extubation failure
  • Fail SAT/SBT if SaO2 <90%, PaCO2 increases >10, failure to initiate breaths, low tidal volumes, resp distress with increasing HR, RR, HTN, work of breathing
  • Causes of failed SBT - etiology of failure not corrected, volume overload, weakness, delirium, anxiety, metabolic
  • Precedex (dexmedetomidine) is a good sedative if agitation limiting extubation - does not sedate as much, helps with anxiety
  • Okay to extubate to NIPPV or HFNC but once on NC and demonstrating post-extubation resp failure, just re-intubate - there is no benefit to NIPPV as rescue therapy (might make it worse)
  • Tracheostomy should be performed once intubated for 14 days if no expectation for timely improvement; can be considered at 7 days if the expectation is intubation >14 days - improves comfort, allows for less sedation, decreased risk of tracheal stenosis
  • Delirium is common in ICU patients and associated with increased mortality, and decreased QOL, and in general is more common when patients on higher sedation
  • Sedation - prioritize propofol and precedex and add benzos if deeper sedation is required or contraindication to propofol; bolus sedation when needed quickly, then transition to drip
  • Propofol - hypotension, bradycardia, and hypertriglyceridemia; accumulates in adipose
  • Precedex - good for anxiolysis, less likely to cause delirium, can cause hypotension, dose-reduce in renal/liver failure
  • Midazolam - benzos increase mortality, delirium, resp depression, and agitation, not great for renal/liver disease
  • Wean precedex 25% q6, wean benzos 25% qday, wean opioids 25% qday 

Trials and Literature

  • HFNC is non-inferior to NIPPV at preventing re-intubation in patients being extubated (JAMA, 2016)
  • NIPPV as rescue after extubation does not prevent the need for re-intubation or reduce mortality (NEJM, 2004)
  • No cuff leak has a positive likelihood ratio of 4; presence of a cuff leak has a negative likelihood ratio ~0.5) (Girard 2017)
  • Early (7d) vs late (14d) trach does not prevent PNA - (JAMA, 2010)
  • Systematic Review of trach timing in ICU - 2015 - early trach leads to increased comfort, less sedation, decreased risk of tracheal stenosis, decreased vent and ICU days